The present invention relates to an industrial process for preparing low-foaming nonionic surfactants and more particularly to a process for preparing ether-capped poly(oxyalkylated) alcohol surfactants which have superior spotting and filming benefits in dishwashing and hard surface cleaning applications, as well as suds suppression in detergent compositions.
Ether-capped poly(oxyalkylated) alcohols can be prepared using various catalysts, such as Lewis acids. However, for industrial production, metallic catalysts, such as stannic chloride is preferred. In addition to being an excellent catalyst for the reaction of a glycidyl ether with ethoxylated alcohol, metallic catalysts are economical and readily available in commercial bulk quantities. They also offer safety and ease of handling advantages on an industrial scale versus alternative catalysts. One important disadvantage for metallic catalysts is that the soluble metallic residue component of the catalyst, such as tin residues when is the catalyst SnCl4, resulting from there use as reaction catalyst, generally cannot be tolerated above about 100 ppm in many cleaning formulations and applications and these residues are difficult and expensive to remove from ether-capped poly(oxyalkylated) alcohol compositions. Successful laboratory approaches to removal of residual metallic catalyst component, such as the use of a silica gel plug and eluting with a 5% methanol in dichloromethane solution leads to complexity and high cost on an industrial production scale. Due to the surfactant properties of the ether-capped poly(oxyalkylated) alcohol, water washing for metallic catalyst component removal leads to emulsification problems leading to complex organicxe2x80x94aqueous separations.
Problems can also arise in the formation of color impurities, caused by the reaction of color forming bodies, in the end product. These color forming impurities or bodies result in a finished product which is undesirable to consumers and consequently unusable because of its appearance. Thus, the synthesis of ether-capped poly(oxyalkylated) alcohol surfactants is not straightforward and can be surprisingly problematic.
Accordingly, the need remains for a simple, inexpensive yet effective process for the production of ether-capped poly(oxyalkylated) alcohol surfactants which does not result in colored impurities in the final product.
U.S. Pat. Nos. 4,272,394, issued Jun. 9, 1981, 5,294,365, issued Mar. 15, 1994, 4,248,729, issued Feb. 3, 1981; 4,284,532, issued Aug. 18, 1981; 4,627,927, issued Dec. 9, 1986; 4,790,856, issued Dec. 13, 1988; 4,804,492, issued Feb. 14, 1989; 4,770,815, issued Sep. 13, 1989; 5,035,814, issued Jul. 30, 1991; 5,047,165, issued Sep. 10, 1991; 5,419,853, issued May 30, 1995; 5,294,365, issued Mar. 15, 1994; GB Application No. 2,144,763, published Mar. 13, 1985; GB Application No. 2,154,599, published Sep. 9, 1985; WO Application No. 9,296,150, published Apr. 16, 1992; WO 94/22800, published Oct. 13, 1994, WO 93/04153, published Mar. 4, 1993, WO 97/22651, published Jun. 26, 1997, EP Application No. 342,177, published Nov. 15, 1989 and xe2x80x9cGlyceryl Bisether Sulfates. 1: Improved Synthesisxe2x80x9d Brian D. Condon; Journal Of the American Chemical Society, Vol. 71, no. 7 (July 1994).
A process for production of ether-capped poly(oxyalkylated) alcohol surfactants which does not result in colored impurities in the final product has been discovered that is simple and economical to practice on an industrial scale. It has been discovered that the use of a basic catalysts, such as Lewis bases, and then following the reaction with a bleaching step can be used to produce poly(oxyalkylated) alcohol surfactants which does not result in colored impurities while avoiding oil and water phase emulsification during work-up and product isolation. This method avoids organic solvents, costly process aids, process complexity and removes the need to remove any metallic catalyst component residues, typically associated with the use of Lewis acid catalysts. This bleaching can be carried out as either a batch or continuous process. Furthermore, the bleached product can be removed in a single or multiple extraction steps.
In accordance with a first aspect of the present invention, a process for preparing an ether-capped poly(oxyalkylated) alcohol surfactant is provided. The surfactant has the formula:
R1O[CH2CH(R3)O]xCH2CH(OH)CH2OR2
wherein R1 and R2 are linear or branched, saturated or unsaturated, aliphatic or aromatic hydrocarbon radicals having from about 1 to about 30 carbon atoms; R3 is H, or a linear aliphatic hydrocarbon radical having from about 1 to about 4 carbon atoms; x is an integer having an average value from 1 to about 30, wherein when x is 2 or greater, R3 may be the same or different, independently H, or C1 to C4 in any given molecule, further wherein when x is 15 or greater and R3 is H and methyl, at least four of R3 are methyl, further wherein when x is 15 or greater and R3 includes H and from 1 to 3 methyl groups, then at least one R3 is ethyl, propyl or butyl, further wherein R2 can optionally be alkoxylated, wherein said alkoxy is selected from ethoxy, propoxy, butyloxy and mixtures thereof. The process comprises the steps of:
(a) providing a glycidyl ether having the formula: 
xe2x80x83wherein R2 is defined as above;
(b) providing an ethoxylated alcohol having the formula: 
xe2x80x83wherein R1, R3 and x are defined as above; and
(c) reacting the glycidyl ether with the ethoxylated alcohol to form the surfactant in the presence of a basic catalyst;
(d) optionally, said surfactant is sparged with an inert gas, preferably N2, Ar and mixtures thereof, optionally under vacuum, preferably a vacuum in the range of 5 to 500 mmHg; and
(e) the product of step (d) is bleached with an about 0.05% to about 5.0%, preferably about 0.1% to about 1.0%, by weight solution of a bleach at a temperature from about 25xc2x0 C. to about 95xc2x0 C.
R1 and R2 are preferably a linear or branched, saturated or unsaturated, aliphatic hydrocarbon radical having from about 6 to about 22 carbon atoms and x is an integer having an average value of from about 6 to about 15.
The step of reacting the glycidyl ether with the ethoxylated alcohol is preferably conducted at a temperature of from about 95xc2x0 C. to about 140xc2x0 C. with 110xc2x0 C. to 130xc2x0 C. even more preferred when alkali metal alkoxylates are employed.
The step of providing the glycidyl ether may further comprises the step of reacting a linear aliphatic or aromatic alcohol having the formula R2OH and an epoxide having the formula: 
wherein R2 is defined as above and X is a leaving group. This reaction may also be conducted in the presence of a catalyst as defined above. The catalyst is typically employed at levels about 0.1 mol % to about 2.0 mol % and the reaction is preferably conducted in the absence of a solvent at temperatures of from about 40xc2x0 C. to about 90xc2x0 C.
As already noted, the surfactants have advantages, including superior spotting and filming reduction benefits as well as excellent greasy soil removal, good dishcare, suds suppression and good overall cleaning.
Accordingly, it is an aspect of the present invention to provide a process for producing a low-foaming nonionic surfactant having superior spotting and filming reduction benefits as well as excellent greasy soil removal, good dishcare, suds suppression and good overall cleaning. It is a further aspect of the present invention to provide a process for producing an ether-capped poly(oxyalkylated) alcohol surfactant. It is a further aspect of the present invention to provide a low-foaming nonionic surfactant produced by the process of the present invention. These and other aspects, features and advantages will be apparent from the following description and the appended claims.
In the description of the invention various embodiments and/or individual features are disclosed. As will be apparent for the skilled practitioner all combinations of such embodiments and features are possible and can result in preferred executions of the invention.
All parts, percentages and ratios used herein are expressed as percent weight unless otherwise specified. All documents cited are, in relevant part, incorporated herein by reference.
Once again, the present invention is directed toward a process for producing a low-foaming nonionic surfactant for use in detergent compositions.
The novel surfactants of the present invention comprise ether-capped poly(oxyalkylated) alcohols having the formula:
R1O[CH2CH(R3)O]x[CH2]kCH(OH)[CH2]jOR2
wherein R1 and R2 are linear or branched, saturated or unsaturated, aliphatic or aromatic hydrocarbon radicals having from about 1 to about 30 carbon atoms; R3 is H, or a linear aliphatic hydrocarbon radical having from about 1 to about 4 carbon atoms; x is an integer having an average value from 1 to about 30, wherein when x is 2 or greater R3 may be the same or different and k and j are integers having an average value of from about 1 to about 12, and more preferably 1 to about 5, further wherein when x is 15 or greater and R3 is H and methyl, at least four of R3 are methyl, further wherein when x is 15 or greater and R3 includes H and from 1 to 3 methyl groups, the n at least one R3 is ethyl, propyl or butyl, further wherein R2 can optionally be alkoxylated, wherein said alkoxy is selected from ethoxy, propoxy, butyloxy and mixtures thereof.
R1 and R2 are preferably linear or branched, saturated or unsaturated, aliphatic or aromatic hydrocarbon radicals having from about 6 to about 22 carbon atoms with about 8 to about 18 carbon atoms being most preferred. Additionally, R2 may be selected from hydrocarbon radicals which are ethoxylated, propoxylated and/or butoxylated. H or a linear aliphatic hydrocarbon radical having from about 1 to about 2 carbon atoms is most preferred for R3. Preferably, x is an integer having an average value of from about 1 to about 20, more preferably from about 6 to about 15.
As described above, when, in the preferred embodiments, and x is greater than 2, R3 may be the same or different. That is, R3 may vary between any of the alkyleneoxy units as described above. For instance, if x is 3, R3may be selected to form ethyleneoxy (EO) or propyleneoxy (PO) and may vary in order of (EO)(PO)(EO), (EO)(EO)(PO); (EO)(EO)(EO); (PO)(EO)(PO); (PO)(PO)(EO) and (PO)(PO)(PO). Of course, the integer three is chosen for example only and the variation may be much larger with a higher integer value for x and include, for example, multiple (EO) units and a much small number of (PO) units. However, when x is 15 or greater and R3 is H and methyl, at least four of R3 are methyl, further wherein when x is 15 or greater and R3 includes H and from 1 to 3 methyl groups, then at least one R3 is ethyl, propyl or butyl.
Particularly preferred surfactants as described above include those that have a low cloud point of less than about 20xc2x0 C. These low cloud point surfactants may then be employed in conjunction with a high cloud point surfactant as described in detail below for superior grease cleaning benefits.
Most preferred according to the present invention are those surfactants wherein k is 1 and j is 1 so that the surfactants have the formula:
R1O[CH2CH(R3)O]xCH2CH(OH)CH2OR2
where R1, R2 and R3 are defined as above and x is an integer with an average value of from about 1 to about 30, preferably from about 1 to about 20, and even more preferably from about 6 to about 18. Most preferred are surfactants wherein R1 and R2 range from about 9 to about 15, R3 is H forming ethyleneoxy and x ranges from about 6 to about 15.
Basically, the alcohol surfactants of the present invention comprise three general components, namely a linear or branched alcohol, an alkylene oxide and an alkyl ether end cap. The alkyl ether end cap and the alcohol serve as a hydrophobic, oil-soluble portion of the molecule while the alkylene oxide group forms the hydrophilic, water-soluble portion of the molecule.
It has been surprisingly discovered in accordance with the present invention that significant improvements in spotting and filming characteristics and, when used in conjunction with high cloud point surfactants, in the removal of greasy soils relative to conventional surfactants, are provided via the ether-capped poly(oxyalkylene) alcohol surfactants of the present invention.
It has been surprisingly discovered that the ether-capped poly(oxyalkylene) alcohol surfactants of the present invention in addition to delivering superior cleaning benefits also provide good suds control. This suds control can be clearly seen in the presence of high sudsing surfactants, such as amine oxides, or in the presence of high sudsing soils, such as proteinaceous or egg soils.
Generally speaking, the ether-capped poly(oxyalkylene) alcohol surfactants of the present invention may be produced by reacting an aliphatic alcohol with an epoxide to form an ether which is then reacted with a base to form a second epoxide. The second epoxide is then reacted with an alkoxylated alcohol to form the ether-capped poly(oxyalkylene) alcohol surfactants of the present invention. The product of the process is a purified mixture of ether-capped poly(oxyalkylene) alcohol surfactants.
The process comprises the first step of providing a glycidyl ether having the formula: 
where R2 is defined as above. Various glycidyl ethers are available from a number of commercial sources including the Aldrich Chemical Company. Alternatively, the glycidyl ether may be formed from the reaction of a linear or branched, aliphatic or aromatic alcohol of the formula R2OH where R2 is defined as above and an epoxide of the formula: 
where X is a suitable leaving group. While a number of leaving groups may be employed in the present invention, X is preferably selected from the group consisting of halides including chloride, bromide, and iodide, tosylate, mesylate and brosylate, with chloride and bromide being even more preferred with chloride being the most preferred (e.g. epichlorohydrin).
The linear or branched alcohol and the epoxide are preferably reacted at ratios ranging from about 0.5 equivalents alcohol to 2.5 equivalents epoxide with 0.95 equivalents alcohol to 1.05 equivalents epoxide more typical. The catalyst is a basic catalyst. The term xe2x80x9cbasic catalystxe2x80x9d, includes within its definition catalysts which are basic. This definition includes both salts, such as KOH, KOtBU, NaOEt, etc., covalent compounds, and elements, such as metallic sodium.
Suitable catalysts include, but are not limited to, alkali metal alkoxylates, such as KOtBu, NaOEt, KOEt, NaOMe and mixtures thereof; NaOH, KOH, CaO, Na and mixtures thereof, more preferably alkali metal alkoxylates. The basic catalyst is preferably a Lewis base. Suitable Lewis base catalysts include, but are not limited to, KOH, NaOCH3, NaOC2H5, KOtBu, NaOH and mixtures thereof. The Lewis base catalysts are preferably employed at amounts of about 0.1 mol % to about 2.0 mol % with about 0.2 mol % to about 1.0 mol % being more typical. The alkali metal alkoxylate catalysts are preferably employed at amounts of about 2.0 mol % to about 20.0 mol % with about 5.0 mol % to about 15.0 mol % being more typical.
While the reaction may be conducted in the presence of a suitable solvent such as benzene, toluene, dichloromethane, tetrahydrofuran, diethylether, methyl tert-butylether or the like, the reaction is preferably conducted neat or in the absence of solvent. When the basic catalyst is an alkali metal hydroxide, it is preferred to include some trace water(typically deionised water), typically less than about 5%, more preferably about 0.2% to about 3%, even more preferably about 0.2% to about 2%, by weight of the reaction mixture. While not wishing to be limited by theory, it is believed that the water aids in the mobility of the hydroxide ions and hence increases the speed of the reaction.
Lastly, the reaction is conducted at temperatures preferably ranging from about 40xc2x0 C. to about 90xc2x0 C., more preferably from about 50xc2x0 C. to about 80xc2x0 C.
The surfactant may be optionally either sparged with an inert gas, preferably, nitrogen, argon or mixtures thereof or placed under a vacuum, to remove any volatile impurities which were formed during the reaction. It is further preferred that the sparging is performed under a vacuum, preferably a vacuum in the range of 5 to 500 mmHg. It is further preferred that the sparging is performed for at least 30 minutes, more preferably at least 90 minutes. It is further preferred that the sparging is performed at a temperature of about 50xc2x0 C. to about 100xc2x0 C., more preferably at a temperature of 60xc2x0 C. to about 70xc2x0 C.
The bleaching step of the present invention may use a bleach or oxidizing agents such as, an oxygen bleach, more preferably hydrogen peroxide, or sodium hypochlorite. It is preferred that any bleach be used at from about 0.05% to about 5.0%, more preferably from about 0.1 to about 1.0 wt % at a temperature from 25xc2x0 C. to 95xc2x0 C. to bleach the resulting reaction product.
To form the surfactant, an ethoxylated alcohol having the formula: 
wherein R1 and x are defined as before in an amount of from about 0.80 to about 2.0 equivalents is combined with the basic catalyst and heated to a temperature ranging from about 50xc2x0 C. to about 95xc2x0 C. and more preferably from about 90xc2x0 C. to about 140xc2x0 C. and more preferably from about 110xc2x0 C. to about 130xc2x0 C. when an alkali metal alkoxylate catalyst is employed. The glycidyl ether is then added to the mixture and reacted for from about 0.5 hours to about 30 hours, more preferably from about 1 hour to about 24 hours.
A further surprising advantage of the present invention is that the use of a basic catalyst avoids the formation of oxygenated impurities which are typically associated with any ethoxylation processes, such as ethanol, ethylene glycol, diethylene glycol, etc. This eliminates any steps necessary to eliminate the removal of these products.
A representative synthetic route is demonstrated via the following diagram and examples. 